The present invention relates to a ball transfer assembly for use in woodworking and sheet metal working.
Cutting large sheets of material e.g. plywood, particle-board, plastic or other heavy cumbersome sheets and keeping them in proper alignment with a saw presents a difficult problem, especially when one person is attempting to manipulate the sheet alone. Friction, when cutting on a table saw or the like, can cause large heavy sheets to stick, jump and jar when advancing the sheet through the blade resulting in a jagged, rough, or irregular cut. For example, a 4'.times.8' sheet of particle board which is 3/4" thick weighs approximately 94 pounds, and a 1 inch thick medium density fibre board is approximately 126 pounds. For one person to manipulate a sheet of this size and weight and maintain an acceptable straight cut to close tolerances is a difficult task.
Generally, wood or other sheet material slides over the flat smooth surface of a table saw or the like by utilizing a saw horse as an extension of the table top itself. This surface, however, is typically rough and relatively large which results in a high amount of friction increasing the possibility of sticking and/or jumping of the sheet material. In order to reduce the friction, auxiliary work supports have been developed which utilize rollers, balls, casters, pneumatics and the like. Problems with such auxiliary work supports, however, still remain. For example, multiple roller conveyer systems are being used as auxiliary work support extensions for table saws but such systems are heavy, difficult to align with the saw, and take up a lot of room in the area surrounding the saw. Such extensions have an additional drawback in that the rollers do not provide 360.degree. movement. Other devices utilize swivel caster wheels. However, swivel caster wheels are not acceptable due to their offset center of radial movement relative to the surface contact area of the wheel with the sheet material being advanced through a saw. Heavy industrial machines utilize ball transfer tables or air flotation valves incorporated into a large high volume system. Again, these types of tables take up a lot of room around the saw and generally cannot be utilized by smaller woodworking operations. In addition, the individual ball transfer units or assemblies which are incorporated into prior ball transfer tables are unitized structures which must be thrown out when dust inhibits the movement of the balls.